One of the most important tests in the construction industry is the Theoretical Maximum Specific Gravity Test, often called the “Rice test.” In this test a sample of loose asphalt mixture is placed in a calibrated container. Water is added to the container to cover the sample. The container is sealed and exposed to 27.5±2.5 mmHg of vacuum pressure. The sealed container is placed on a shaker and shaken under the 27.5±2.5 mmHg of vacuum pressure for 15 minutes. Shaking along with vacuum helps ensure that air and trapped air bubbles are removed from the sealed container. After 15 minutes of shaking, the container is allowed to come back to atmospheric pressure. The calibrated container is then submerged in a water tank equipped with a scale and a submerged or underwater weight of the container and sample is determined. Knowing the initial dry weight (mass) of the sample (A), underwater mass of the container (B) and submerged total weight of the container and sample (C), maximum specific gravity of the asphalt mixture can be determined using the below equation.
      Theoretical    ⁢                  ⁢    Maximum    ⁢                  ⁢    Specific    ⁢                  ⁢    Gravity    =      Gmm    =                  A                  A          -                      (                          C              -              B                        )                              .      
This test procedure is covered under American Society of Testing and Materials (ASTM) D2041 standard and American Association of State Highway and Transportation Officials (AASHTO) T209 standard. These test standards provide alternative ways of measuring the weights of samples after vacuum operation and suitable containers for the test. The results from the test are used throughout the mixture design process for asphalt pavements and for determination of total air void content in compacted asphalt in the laboratory and the field. In almost all pavement jobs, percent air void is a quality control measure for compaction and can be used for acceptance and rejection of a pavement job or batch.
Limitations related to this test are manual adjustment of the vacuum level, the precise time when the shaker is turned on when vacuum approaches the nominal value, the precise amount of time the shaker is left on, and the frequency and quality of shaking instruments used. All these factors can affect the accuracy of the test and repeatability of results, particularly between different users and/or testing facilities.